In recent years, improvements in performance and cost reductions for color copiers, color printers, and color scanners have contributed to creating an environment in which high quality illegal documents and copies, including paper currency, negotiable securities, and even gift certificates, can be easily created.
Data flow in a typical output system according to the related art is shown in FIG. 11. This output system comprises a computer 50 and a printer 60 connected to the computer 50. The computer 50 includes an operating system (OS) 52 and hardware 55 that operates according to control data from the OS 52. The OS 52 provides the computer 50 with various functions, including the abilities to display information on a screen, and create and store documents.
The OS 52 includes printer driver software (“printer driver” below) 53 for printer control independently of the operating system kernel, and a part of OS 52 is provided for an application programming interface (API) 54. The API 54 provides an interface to access operating system functions under the OS 52, in response to various requests from application programs (“APPLICATION A” and “APPLICATION B” in FIG. 11)
There are generally two methods used to print in an output system having a computer controlled by a general-purpose operating system. In one method, shown in FIG. 11 as printing from APPLICATION A, the printer driver 53 and API 54 are sequentially called in response to a print request from the application program, and the print data is generated by the printer driver 53 and sent to the printer I/O interface 56 of the hardware 55. The other method, shown as printing from APPLICATION B, does not use the printer driver 53 to generate the print data, but rather sends data from the application program through the API 54 directly to the printer I/O interface 56 of the hardware 55.
The conventional method for preventing illegal printing and copying in such an output system has been to build an illegal printing/copying prevention function into the printer driver 53. With the output system described above, however, this function can be easily bypassed. That is, if the processing content on printer 60 is decrypted by analyzing data output from computer 50, for example, if the data to be printed is compressed on computer 50 and then expanded on printer 60 and so on, printer 60 can be directly accessed by the application programs without using printer driver 53 to generate the print data. Therefore, illegal printing and copying cannot be prevented using this print route.
It should be noted that color copier is bound to equip an illegal printing/copying prevention function today. The means for implementing this function is generally provided in the form of hardware, and an increase in product cost is therefore unavoidable.
Furthermore, when an illegal printing/copying prevention function is provided as a hardware component on the printer side in a system including plural computers and plural printers accessible to the plural computers via a LAN or other network, the same hardware must be disposed to each individual printer. This is wasteful and unnecessarily expensive.
An object of the present invention is to provide a low cost, secure output system and output method used in the same, and a data storage medium storing a program run on this output system.